This invention pertains generally to tracking and guidance systems, and particularly to systems wherein radar signals from a transmitter are utilized to control an intercept of a target by a missile.
It is known in the art that so-called "semiactive" tracking and guidance systems have wide application for controlling the intercept of a target by a missile. A "semiactive" system is one in which both a target of interest and a missile are illuminated with radio frequency energy from a radar. A portion of the energy reflected from the target is received at the missile along with energy directly transmitted from the radar. Upon processing of such signals in the missile, guidance signals are produced which cause the missile to intercept the target. The guidance signals are azimuth angle, elevation angle and their rates and target-missile closing velocity.
While a semiactive system maintains its accuracy and dependability to the maximum range of the radar, experience has proven that operating conditions may present difficulties which mitigate against performance at all times. Major operating conditions which mitigate against performance are feedthrough, ground clutter return and noise. The return clutter signals and noise are processed in combination with the target tracking signals so that large amounts of return clutter tend to saturate processing elements. This saturation affects the linearity of the receiver, and thereby can cause an incorrectable error or degradation in the measured directional information.